Mincing machine

ABSTRACT

A mincing machine having at least one perforated disc and relatively rotatable blade means operably associated with said disc. The blade means are carried by a blade-holder which is axially displaceable relative to the perforated disc. Biasing means for biasing the blade-holder towards the disc so that the blades are resiliently pressed against the disc surface.

United States Patent [56] References Cited UNITED STATES PATENTS3,076,489 2/1963 Schmidt et al 146/182 3,340,917 9/1967 Vedvik 146/1823,404,715 10/1968 Kielsmeier 146/192 FOREIGN PATENTS 1,167,214 4/1964Germany 146/192 Primary Examinerwillie G. Abercrombie Attorney-Olson,Trexler, Wolters and Bushnell ABSTRACT: A mincing machine having atleast one perforated disc and relatively rotatable blade means operablyassociated with said disc. The blade means are carried by a blade-holderwhich is axially displaceable relative to the perforated disc. Biasingmeans for biasing the blade-holder towards the disc so that the bladesare resiliently pressed against the disc surface.

PATENTEUJUHZZIBYI 35 6,0233

sum 3 0r 4 Inventor.- fdlw Aw rzer MINCING MACHINE BACKGROUND OF THEINVENTION The invention relates to a mincing machine, preferably formeat. The invention is particularly concerned with a mincing machinehaving at least one perforated disc over which knifeblades rotate; theblades are movably held in a multiarmed knife-head and resilientlypressed against the perforated disc, those surfaces of the arms of theknife-head which are to the front in the circumferential direction beingat an acute angle to the surface of the perforated disc.

Such a mincing machine is shown in German Pat. specification No. I167214. The fact of the knife-blades of this mincing machine, being heldin movable fashion, and being resiliently pressed against the perforateddisc, compensates for departures from the parallel relative attitude ofthe knife-head and perforated disc, unless those departures have beenintentionally introduced as a result of the perforated disc beingobliquely set or have occurred unintentionally in consequence oftolerances in production and assembly, and guarantees that theknife-blades exert substantially constant pressure on the perforateddisc under all conditions and circumstances of operation. This reducesfrictional wear, the more so since the spring biased knife-blades can toa certain extent avoid particularly hard bone and gristle components inthe material being minced, and such components need not be completelyminced immediately upon first being picked up.

It has however now appeared that the knife arrangement of German Pat.specification No. I 167214 is disadvantageous to the extent that theknife-blades which are individually and movably guided and sprung inslits in the knife-head easily become jammed if any of the materialbeing minced sticks in the slits and on the spring biasing elements. Theknife-blades are then no longer capable of developing their actiondescribed above.

A mincing machine according to the invention has at least one perforateddisc and a multiarmed knife-head mounted for rotation adjacent the discand comprising a precutter which is substantially axially fixed relativeto the disc and which has arm elements constituting the leading parts ofthe knife-head arms and having leading faces at an acute angle to thesurface of the disc, a blade-holder which is axially displaceablerelative to the precutter and the disc and which has arm elementsconstituting the trailing parts of the knife-head arms, knifebladescarried by the blade-holder arm elements between the precutter andblade-holder arm elements, and biasing means for biasing theblade-holder toward the disc so that the blades are pressed against theblade surface.

Since the biasing means may readily be arranged so that it is notexposed to the action of the material being minced, there is no dangerof the springing of the knife-blades being obstructed. In thisconnection, the fact that the knife-head is separated into the precutterand blade holder preserves unaf fected the axial relative attitude orthose front surfaces of the arms of the knife-head which are disposedobliquely with respect to the perforated disc, and which set up apumping action which conveys the material being minced through themachine, while the blade-holder together with the knifeblades can moveaxially in relation to the precutter.

Automatic adaption of the knife-blades to the position of the perforateddisc is further encouraged if, as is preferred, the blade-holder isarranged to rock slightly on the driving shaft.

The arrangement according to the invention has a particularlyadvantageous effect when applied to mincing machines having a pluralityof knife-heads and perforated discs. While it has hitherto beennecessary to take care that mutual clearances between the knife-headswere exactly equal to the clearances between the associated perforateddiscs, the arrangement according to the invention may not involve thenecessity for any rigid corltmon alignment of the individual mincingstages. It is therefore "readily possible for unskilled hands to puttogether the individual parts after the replacement of worn parts orafter cleaning.

If there is a plurality of knife-heads sequentially arranged on onedriving shaft, a further development of the invention involves theprecutters being clamped fast against one another, while the biasingmeans exerting pressure on the blade-holders are in each case supportedon the neighboring precutter or shaft-termination. It has transpiredthat in the case of such an arrangement there is a continuousventilation path along the driving shaft where the air aspirated withthe material being minced collects because of its low specific weight.

Above all in the case of such a multistage arrangement, effectiveventilation of the material being minced can be encouraged by placingthe space in the region of the hub between the precutter and theblade-holder in communication with suction.

The biasing means which exert pressure on the blade-holder may be aspiral spring concentric with the driving shaft. However, it may also bea gas-filled annular space concentrically surrounding the driving shaftand subjected to externally adjustable pressure, of for example a liquidunder pressure. The latter form of biasing means may with advantage havecontrol means so arranged that there is no pressure in the annular spacewhen the machine is idling, and the material entering the machineactuates a switching member which enables a predetermined workingpressure to take effect in the annular space.

It is known that the knife-blades of the high-speed knifehead ought notto be pressed against the perforated disc without the cooling action ofcooked meat running through. Mechanical constructions enabling theknife-head to be manually withdrawn from the perforated disc in theabsence of any material for mincing entering the machine have thereforealready been proposed. The method according to the invention ofcontrolling the pressure in an annular space filled with gas and ifdesired also with liquid, and acting on the blade-holder, solves thisproblem in a better way, the more so since the control means may beregulated in direct dependence on the entry of material for mincing intothe machine, the material actuating a pressure-switch or mechanicalswitch.

The invention will be more readily understood by way of example from thefollowing description of a meat-mincing machine in accordance therewith,reference being made to the accompanying driving in which:

FIG. I is a side view of a three-stage meat mincing machine, the upperhalf being shown in axial section,

FIG. la is a section along the line A-B in FIG. 1,

FIG. 2 is a plan view of the knife-head and perforated disc or a mincingstage,

FIG. 3 is a perspective exploded view of the parts shown in FIG. 2, and

FIG. 4 is a sectional view corresponding to FIG. 1 but on an enlargedscale through the first mincing stage, but with a modified biasingarrangement, a preferred form of control means for said modifiedarrangement being illustrated schematically.

As shown in the drawings, the mincing machine has a cylindrical housingI of the mincing stages within which are mounted three perforated discs2 spaced away from one another, and having perforations of decreasingdiameter and increasing number in the direction in which the materialbeing minced is conveyed (arrow 3). The discs 2 are spaced by cuttingrings 4 which are in the form of cylindrical sleeves with inwardlyprojecting teeth 5, and which abut the discs 2 adjacent theirperipheries, the assembly of discs and cutter rings being clamped withinthe housing I between a rib formed at the forward end of the housing anda nut 6. Each of the discs 2 has a knife-head designated as a whole by8, and having a knife-blade 9 bearing against the associated disc 2. Thethree knife-heads 8 are arranged on a shaft 7 running coaxially in thehousing I, and having the cross-sectional shape shown in FIG. la; thebearings for the shaft are not illustrated. Each knife-head 8 consistsessentially of a precutter l0 and a bladeholder 11, of which the hollowhubs l2 and 13 respectively fit concentrically one into the other (FIGS.2 and 3). As best shown in FIG. 2, each knife-head has three arms ofeach of which the leading element is a component of the precutter andthe trailing element 116 is a component of the blade-holder llll. InFIG. 3, the precutter is illustrated by only the hub lit) with itsannular shoulder 114 at one end and the outermost tip of the front part115 of one arm of the knife-head projecting beyond the associated rearpart 16.

The hub 12 of each precutter 110 has cutaways 17 in whichcorrespondingly shaped portions 118 of the arm elements 16 of theknife-head arms fit (FIG. 3). As shown in FIGS. l and la, the shoulderT4 of each hub 12 has a bore shaped similarly to the polygonal crosssection of the shaft 7, so that the precutters are rotated with theshaft; on the other hand, the bore a in the corresponding shoulder 20 ofthe hub 13 of each bladeholder III is larger than the maximum shaftdiameter and the blade-holders are therefore not linked intorque-transmitting manner with the shaft 7. On the outside of the hub13 of each blade-holder llll there are projecting radial segments 1130which are shown in FIG. la and which engage the interior of hub 12 andtherefore keep the blade-holder concentric while leaving a certainamount of play for compensating for production tolerances. When theshaft 7 rotates, the blade-holder 111 is moved with the precutter 10 byvirtue of the engagement of the edges of the cutaways 17 with theportions B8 of the rear arms 16 of the knife-head; as a result there isa positive driving link between each precutter W and its blade-holderill. The driving link between the precutter 10 and the shaft 7 may alsobe set up, as the modification illustrated in FIGS. 2 and 3 shows, by aspring fitting on the shaft 7 and a groove 19 surrounding the latter inthe shoulder 14 of the precutter hub l2.

As FIG. I particularly reveals, the cutaways 17 in the hollow hub 112 ofthe precutter it) are deeper in the axial direction than the height ofthe portions 18 of the trailing arm elements 16 of the knife-head arms.This gives the blade-holder ill a certain amount of axial mobility inthe precutter I19. This mobility is unhindered by the clamping of thethree hubs 12 of the precutters 110 against one another between ashoulder 2ll on a rotary pump wheel22 and a ring nut 23; this wheel 22sets up suction downstream of the mincing stages and ejects from themachine the minced material emerging through the perforated disc 2 ofthe last stage.

Thus while the precutters 1 .0 are held against axial movement relativeto the shaft 7, the blade-holders Ill are capable of axial displacementsince each is disposed with some play in the hubs 112 of the associatedprecutter and therefore on the shaft 7; each blade-holder 11 can alsorock to some extent. However, a spiral spring 24 inserted between theshoulder 20 of the hub 13 of each blade-holder ill and the shoulder 14of the hub 12 of the neighboring precutter W or the ring 23, andconcentrically surrounding the shaft 7, presses each bladeholder Illagainst the associated perforated disc 2. As a result, the knife-blades9 of each knife-head bear against the associated perforated disc 2.

The knife-blades 9 are mounted by means of holes 25 on pins 26projecting in the circumferential direction from those surfaces of therear arm elements 16 of the blade-holder llil that are to the front inthe direction of rotation 27. The slit formed between the arm elements16 of the blade-holder H and the arm elements 115 of the precutter 10 issufficiently narrow to prevent the knife-blades 9 from dropping off thepins 26, but sufficiently wide to ensure that the knifeblades 9 canpivot unhindered on their pins. Grooves 28 in those surfaces of the armelements 15 are to the rear in the direction of rotation, and thatfacing the knife-blades 9, ensure the dispersal of any material beingminced that may penetrate between the knife-blades 9 and those surfacesof the elements 15.

Accordingly, through the resilient biasing action of spring 24, thepivotal mounting of blades 9 and the ability of bladeholder assembly illto rock slightly, the blades 9 may adjust to avoid particularly hardbone and gristle components in the material being minced. This abilityof the blades 9 to adapt, materially reduces the frictional wearthereon.

The leading surfaces 29 of the leading arm elements 15 of the precutterI0 extend in known manner obliquely to the perforated disc 2. They areadvantageously followed by a surface 39 extending substantially parallelto the perforated disc 2 and retaining the material to be minced thathas collected by the oblique surfaces 29 until it is minced by theknife-blades 9 in conjunction with the perforations in the associateddisc 2, so that the material is prevented from dancing in front of theknife-blades 9. The space 31 between the hubs of the precutter B0 andthe associated blade-holder 111 of the last knife-head 8 (at the left inFIG. ll) may be placed in communication with suction via a bore 32passing through the hubplate of the pump rotor 22, so that the air whichcollects in the hub region of that knife-head 8 is aspirated off. FIG. Bshows similar bores for the other two knife-heads 8 passing through thehubs 114 so that the spaces 31 of all the mincing stages are incommunication parallel to the shaft 7.

FIG. 4 shows a cutaway portion of a modified design of the means ofresiliently pressing the blade-holder 111 against the perforated disc 2.Instead of the spiral spring 24 of FIGS. 11 and 2, a pistonlike,pressure operated arrangement is employed. As can be seen in FIG. 4, anannular air-filled ring 33 is disposed against the shoulder 20 of thehollow hub 13 of the blade-holder ill. The ring 33 is accommodated in anannular space 34 defined internally by the shaft 7 and externally by thehub 13, on one face by the shoulder 20 and on the other face by a sleeve35 inserted into the hollow hub 13. Said sleeve 35 abuts against thering 23 to limit axial movement thereof in one direction. The sleeve 35carries annular sealing elements 40 and 42, which engage the inner boreof the hub 13 and the external surface of shaft 7, respectively. Inaddition, shoulder 20 may carry an annular packing member 44 whichsealingly engages shaft 7. Accordingly, it may be seen that the annularspace 34 is substantially fluidtight, except for its communication witha source of fluid under pressure, as will be detailed hereinafter. Also,ring 33 includes annular sealing lips 36 to insure that pressurizedfluid does not leak past said ring.

Annular. space 34 communicates with a source of fluid under pressure viaan axial shaft bore 37 and a transverse bore 38. Thus, upon theintroduction of fluid under pressure into the annular space 34, thefluid will exert an axial force on shoulder 29 via the ring 33, whichforce is effective to move the balde-holder 111 and its associatedblades 9 toward and against the perforated disc 2. lf the pressurizedfluid is withdrawn from the chamber 34 or the pressure head in saidchamber is reduced in some other manner, the blades 9 will not be forcedinto engagement with the disc 2 and will move freely therepast. Thus,since the meat being processed provides a cooling action for blades 9,once processing thereof is completed the pressure in annular space 34 isreduced to avoid undue wear on blades 9.

As was the case with the previously discussed embodiment, the blades 9of the embodiment of FIG. 4 may also adapt, so that they can to acertain extent avoid hard bone and/or gristle. This is accommodated forby providing that the biasing force exerted by the pressurized fluid issuch as to permit slight retraction of the blade holder l1 when bone orgristle is encountered.

The particular fluid employed to move the blade-holder it is a matter ofchoice, water, air pressure or the like being anticipated.

A preferred control system for the pressure operated arrangement justdescribed is illustrated schematically in FIG. 4. In this regard, aswitch 46 is positioned within the mouth or entry portion of a hopper 48that is associated with the mineing machine of the present invention.The switch 46 is normally opened and positioned such that it will beactuated by material being introduced into hopper 48, which engagementbiases the switch to the closed condition. Once switch 46 is closed,solenoid 5'1) is placed in circuit with a source of power 52 to energizethe solenoid coil, and move the solenoid actuator rod 54 downwardly. Theactuator rod 54 is operably joined to a piston member 56 of a fluidcylinder arrangement 58 to effect movement thereof in the directionindicated. The fluid cylinder 53 has an outlet port 69 whichcommunicates with a fluid line 62 which in turn is associated with theshaft bore 37. Accordingly, upon energization of solenoid 50, piston 56will move downwardly forcing fluid out of cylinder 58, thus increasingthe fluid pressure in line 62 and correspondingly, in the annular space34 via bores 37 and 38.

While the material to be processed engages switch 46, the circuit tosolenoid 50 will be closed and the blades 9 biased into engagement withdiscs 2. Since it is desirable for the biasing of blades 9 to continueafter the last portion of material passes switch 46, so that the mincingprocess may be completed, switch 46 is preferably of a type which willremain closed for a short period of time after engagement by material inhopper 48 ceases. A wide variety of switches of this type are available,as are other means for effecting the same end result, and furtherexplanation is not deemed necessary.

In the example or embodiment illustrated, the knife-heads 8 have threearms, but it is to be understood that each knifehead may have two ormore than three arms as required. Also, it is envisioned that variousother changes, modifications and substitutions may become readilyapparent to one skilled in the art from the foregoing description. It isintended that said modifications or changes shall be within the scope ofthe present invention insofar as they are encompassed by the claimsappended hereto.

The invention I claim is as follows:

1. A mincing machine including; at least one perforated disc; amultiarmed knife-head mounted adjacent said disc for relative rotationtherebetween, and said knife-head comprising, a blade-holder which isaxially displaceable relative to said disc, a plurality of knife-bladescarried by said bladeholder, and a precutter which is substantiallyaxially fixed relative to the disc and which has arm elementsconstituting the leading parts of the knife-head arms and having leadingfaces at an acute angle to the surface of said disc, said blade-holderbeing axially displaceable relative to said precutter and having armelements constituting the trailing parts of the knife-head arms, saidprecutter and blade-holder arm elements carrying the knife-bladestherebetween; and biasing means for biasing the blade-holder and itsassociated blades axially toward said disc such that said blades areresiliently pressed against the disc surface.

2. A mincing machine as defined in claim 1 wherein the blade-holder ismounted for slight rocking movement relative to said disc.

3. A mincing machine as defined in claim 1 wherein the knife-blades arepivotably carried by the blade-holder.

4. A mincing machine as defined in claim 1, wherein both the precutterand the blade-holder have hollow hubs, the precutter hub coaxiallysurrounding the blade-holder hub which has projecting elementsthereon'engaging in recesses fon'ned in said precutter hub, whereby saidprecutter and blade-holder will rotate together with relative axialmovement therebetween being permitted.

5. A mincing machine as defined in claim 4, wherein said machineincludes a driving shaft, said shaft having the precutter nonrotatablyaffixed thereto, whereby said precutter will drive the blade-holder bymeans of the interengaged projecting elements and recesses on saidprecutter and said bladeholder.

6. A mincing machine as defined in claim 4, wherein the space betweensaid coaxial hubs on the precutter and bladeholdcr, respectively,communicates with suction.

7. A mincing machine according to claim 1, wherein the blade-holderincludes a hub and a radially inwardly extending flange against whichthe biasing means acts to resiliently press the blades against the discsurface.

8. A mincing machine as defined in claim 7, wherein said biasing meansis a spiral spring engaging said radially inwardly extending shoulder onthe blade-holder hub.

9. A mincing machine according to claim I, wherein said biasing meansincludes a fluid-operated arrangement.

10. A mincing machine as defined in claim 9, wherein said fluid-operatedarrangement includes: a radially inwardly extending annular flange onsaid blade-holder, structure cooperating with said flange to define anannular enclosed space; sealing means for rendering said spacesubstantially fluidtight; and fluid conduit means in communication withsaid space and adapted to be connected to a source of fluid underpressure whereby upon the introduction of fluid under pressure into saidspace said axial movement of the bladeholder relative to the disc may beeffected.

11. A mincing machine as defined in claim 10, wherein saidfluid-operated arrangement includes an annular, air-filled ring disposedin engagement with said inwardly extending flange on the blade-holder,and upon which fluid under pressure will act for transmission of axialforce to said flange.

12. A mincing machine as defined in claim 9, further including controlmeans for activating said fluid-operated arrangement upon material beingminced entering said machine.

13. A mincing machine including: at least one perforated disc; amultiarmed knife-head mounted adjacent said disc for relative rotationtherebetween, and said knife-head comprising, a blade-holder which isaxially displaceable relative to said disc and includes a plurality ofknife-blades; remotely controlled biasing means for biasing theblade-holder axially into engagement with said disc, said remotelycontrolled biasing means including sensing means operated by entry ofmaterial to be minced into said machine to actuate said bias ing means.

14. A mincing machine including: at least one perforated disc; amultiarmed knife-head mounted adjacent said disc for relative rotationtherebetween, and said knife-head including a blade-holder which isaxially displaceable relative to said disc, a plurality of knife-bladescarried by said blade-holder, and a precutter which is substantiallyaxially fixed relative to the disc and which has arm elementsconstituting the leading parts of the knife-head arms and having leadingfaces at an acute angle to the surface of said disc, said blade-holderbeing axially displaceable relative to said precutter and having armelements constituting the trailing parts of the knife-head arms, saidprecutter and blade-holder arm elements carrying the knife-bladestherebetween; and means defining an annular space between said precutterand said blade-holder and adapted upon the introduction of fluid underpressure into said space to bias said blade-holder axially to engagesaid disc; and control means for selectively applying liquid underpressure to said annular space.

15. A mincing machine as defined in claim 14, wherein said control meansincludes; sensing means operated by entry of material to be minced intosaid mincing machine; means for applying liquid under pressure to saidannular space; and means operated by said sensing means for actuatingsaid applying means.

16. A mincing machine including: at least one perforated disc; amultiarmed knife-head mounted adjacent said disc for relative rotationtherebetween, and said knife-head comprising, a blade-holder which isaxially displaceable relative to said disc, and a plurality ofknife-blades carried by said bladeholder; and biasing means for biasingthe blade-holder and its associated blades axially toward said disc suchthat said blades are resiliently pressed against the disc surface, saidbiasing means including a fluid-operated arrangement, said arrangementincluding a radially inwardly extending annular flange on saidblade-holder, structure cooperating with said flange to define anannular enclosed space, sealing means for rendering said spacesubstantially fluidtight, and fluid conduit means in communication withsaid space and adapted to be connected to a source of fluid underpressure whereby upon the introduction of fluid under pressure into saidspace said axial movement of the blade-holder relative to the disc maybe effected.

17. A mincing machine as defined in claim 16, wherein saidfluid-operatedarrangement includes an annular, air-filled ring disposedin engagement with said inwardly extending flange on the blade-holder,and upon which fluid under pressure will act for transmission of axialforce to said flange.

18. A mincing machine as defined in claim 16, further including controlmeans for activating said fluid-operated arrangement upon material beingminced entering said machine.

1. A mincing machine including; at least one perforated disc; amultiarmed knife-head mounted adjacent said disc for relative rotationtherebetween, and said knife-head comprising, a bladeholder which isaxially displaceable relative to said disc, a plurality of knife-bladescarried by said blade-holder, and a precutter which is substantiallyaxially fixed relative to the disc and which has arm elementsconstituting the leading parts of the knife-head arms and having leadingfaces at an acute angle to the surface of said disc, said blade-holderbeing axially displaceable relative to said precutter and having armelements constituting the trailing parts of the knife-head arms, saidprecutter and blade-holder arm elements carrying the knife-bladestherebetween; and biasing means for biasing the blade-holder and itsassociated blades axially toward said disc such that said blades areresiliently pressed against the disc surface.
 2. A mincing machine asdefined in claim 1 wherein the blade-holder is mounted for slightrocking movement relative to said disc.
 3. A mincing machine as definedin claim 1 wherein the knife-blades are pivotably carried by theblade-holder.
 4. A mincing machine as defined in claim 1, wherein boththe precutter and the blade-holder have hollow hubs, the precutter hubcoaxially surrounding the blade-holder hub which has projecting elementsthereon engaging in recesses formed in said precutter hub, whereby saidprecutter and blade-holder will rotate together with relative axialmovement therebetween being permitted.
 5. A mincing machine as definedin claim 4, wherein said machine includes a driving shaft, said shafthaving the precutter nonrotatably affixed thereto, whereby saidprecutter will drive the blade-holder by means of the interengagedprojecting elements and recesses on said precutter and saidblade-holder.
 6. A mincing machine as defined in claim 4, wherein thespace between said coaxial hubs on the precutter and blade-holder,respectively, communicates with suction.
 7. A mincing machine accordingto claim 1, wherein the blade-holder includes a hub and a radiallyinwardly extending flange against which the biasing means acts toresiliently press the blades against the disc surface.
 8. A mincingmachine as defined in claim 7, wherein said biasing means is a spiralspring engaging said radially inwardly extending shoulder on theblade-holder hub.
 9. A mincing machine according to claim 1, whereinsaid biasing means includes a fluid-operated arrangement.
 10. A mincingmachine as defined in claim 9, wherein said fluid-operated arrangementincludes: a radially inwardly extending annular flange on saidblade-holder, structure cooperating with said flange to define anannular enclosed space; sealing means for rendering said spacesubstantially fluidtight; and fluid conduit means in communication withsaid space and adapted to be connected to a source of fluid underpressure whereby upon the introduction of fluid under pressure into saidspace said axial movement of the blade-holder relative to the disc maybe effected.
 11. A mincing machine as defined in claim 10, wherein saidfluid-operated arrangement includes an annular, air-filled ring disposedin engagement with said inwardly extending flange on the blade-holder,and upon which fluid under pressure will act for transmission of axialforce to said flange.
 12. A mincing machine as defined in claim 9,further including control means for activating said fluid-operatedarrangement upon material being minced entering said machine.
 13. Amincing machine including: at least one perforated disc; a multiarmedknife-head mounted adjacent said disc for relative rotationtherebetween, and said knife-head comprising, a blade-holder which isaxially displaceable relative to said disc and includes a plurality ofknife-blades; remotely controlled biasing means for biasing theblade-holder axially into engagement with said disc, said remotelycontrolled biasing means including sensing means operated by entry ofmaterial to be minced into said machine to actuate said biasing means.14. A mincing machine including: at least one perforated disc; amultiarmed knife-head mounted adjacent said disc for relative rotationtherebetween, and said knife-head including a blade-holder which isaxially displaceable relative to said disc, a plurality of knife-bladescarried by said blade-holder, and a precutter which is substantiallyaxially fixed relative to the disc and which has arm elementsconstituting the leading parTs of the knife-head arms and having leadingfaces at an acute angle to the surface of said disc, said blade-holderbeing axially displaceable relative to said precutter and having armelements constituting the trailing parts of the knife-head arms, saidprecutter and blade-holder arm elements carrying the knife-bladestherebetween; and means defining an annular space between said precutterand said blade-holder and adapted upon the introduction of fluid underpressure into said space to bias said blade-holder axially to engagesaid disc; and control means for selectively applying liquid underpressure to said annular space.
 15. A mincing machine as defined inclaim 14, wherein said control means includes; sensing means operated byentry of material to be minced into said mincing machine; means forapplying liquid under pressure to said annular space; and means operatedby said sensing means for actuating said applying means.
 16. A mincingmachine including: at least one perforated disc; a multiarmed knife-headmounted adjacent said disc for relative rotation therebetween, and saidknife-head comprising, a blade-holder which is axially displaceablerelative to said disc, and a plurality of knife-blades carried by saidblade-holder; and biasing means for biasing the blade-holder and itsassociated blades axially toward said disc such that said blades areresiliently pressed against the disc surface, said biasing meansincluding a fluid-operated arrangement, said arrangement including aradially inwardly extending annular flange on said blade-holder,structure cooperating with said flange to define an annular enclosedspace, sealing means for rendering said space substantially fluidtight,and fluid conduit means in communication with said space and adapted tobe connected to a source of fluid under pressure whereby upon theintroduction of fluid under pressure into said space said axial movementof the blade-holder relative to the disc may be effected.
 17. A mincingmachine as defined in claim 16, wherein said fluid-operated arrangementincludes an annular, air-filled ring disposed in engagement with saidinwardly extending flange on the blade-holder, and upon which fluidunder pressure will act for transmission of axial force to said flange.18. A mincing machine as defined in claim 16, further including controlmeans for activating said fluid-operated arrangement upon material beingminced entering said machine.